For a study out in this week’s Proceedings of the National Academy of Sciences, Dean Mobbs and colleagues put their subjects through this fright fest to sort out how the brain responds to different parts of a threat. It’s not all about the presence of a creepy crawler, Mobbs found—it’s whether that creepy crawler is creeping closer.

As the spider advanced, MRI scans allowed researchers to see flashes of activity switch from the volunteer’s prefrontal cortex – a region associated with anxiety – to a spot in the midbrain known to involve intense fear. But the neural terror waned when the tarantula retreated, “regardless of the spider’s absolute proximity,” wrote the study’s authors. In other words, as long as the spider was moving away, no matter how close it still was, the volunteers relaxed. [MSNBC]

If there’s a certain smell or sound that instantly brings back traumatic memories, it could be because those memories are stored—at least in part—in brain regions associated with the input of your senses, according to a study this week in Science.

Neuroscientist Benedetto Sacchetti went looking in rat brains for the neural connections between the senses and intense memories.

Each sense, including sound, smell and vision, has a primary and a secondary sensory cortex area in the brain. The primary cortex sends sensory information to the secondary cortex, which then connects to emotional and memory areas of the brain [Science News].

It’s the essence of instinct: If you take a lab mouse who has never caught a glimpse of a cat and waft a little eau de feline towards it, the mouse will freeze in fear, and will then back away from the source of the odor. Now researchers have pinned down the chemical signals the mice are reacting to–and have shown in the process a fascinating new form of inter-species communication.

Mice have a specialized organ in their noses that picks up chemical signals, called the vomeronasal organ, which helps them detect pheromones emitted by other mice. These mice pheromones have a direct effect on behavior–most obviously in the realms of mating and fighting. In this new study, published in the journal Cell, neurobiologist Lisa Stowers decided to investigate whether the vomeronasal organ was capable of picking up signals from other species as well.

Whether your fear is panicked, like in a life-or-death situation, or deliberative, like a decision about whether to take a big risk on game show, it all comes back to the amygdala. And a new study of patients with lesions on the amygdala, reported by Caltech scientists in the Proceedings of the National Academy of Sciences, suggests that damage to our brain’s fear center might turn people into reckless gamblers.

The researchers found two women with Urbach-Wiethe disease, which results in damage to the almond-shaped amygdala. Benedetto De Martinoa and his team paired those two with 12 people with undamaged brains, and presented everyone with a series of gambling tests. The study found that healthy volunteers would only opt to gamble if the potential gains were one and a half to two times the size of the potential losses [BBC News]. The women with Urbach-Wiethe, however, would keep rolling the dice as the odds got worse, and in some cases would even play if the potential loss was greater than the potential gain.

When people breathe in carbon dioxide, they start to panic. It happens in mice and other animals, too, as the body responds to the threat of suffocation. Now, in a study in Cell, researchers have connected a particular gene to that response in the brain.

The gene, called ASIC1a, is connected to a protein found in abundance in the amygdala, the area scientists believe to be the brain’s fear center. In their new study … the researchers show that mice lacking this gene don’t freeze in place–a commonly used indicator of rodent fear–to the extent that normal mice do when the team pumped CO2 into their enclosure. But when Wemmie and colleagues injected a virus containing the ASIC1a gene into the amygdala of the mice, they acted like normal mice, freezing up when exposed to elevated CO2 [ScienceNOW Daily News].

A mouse’s nose has a cluster of specialized cells that respond to the chemical signals sent out by fellow mice that are in distress, researchers report, meaning that mice can literally smell fear. A lump of nerve cells in the nose tip called the Grueneberg ganglion responds to the “fear pheromones” of imperiled creatures, sending a signal straight to the brain. As Grueneberg ganglia are known to exist in rodents, cats, apes, and humans, researchers say it’s likely that the cells perform the same function in all mammals.

In a new study, researchers dosed water dishes with mouse alarm pheromones, and put the dishes in cages with both normal mice and mice whose ganglia had been removed. The contrast was very striking, [lead researcher Marie-Christine] Broillet said. “The normal mouse immediately gets scared and goes to the corner of the box and freezes,” she said. But mice without the ganglia carried on as before, seemingly unaware of the danger signals. Both groups were able to sniff out cookies hidden in their cages, however, suggesting the altered group’s sense of smell was otherwise unaffected [National Geographic News].

When confronted with something truly terrifying (say, for example, an irritated grizzly bear), most human faces assume the same expression, with bulging eyes and flaring nostrils. Researchers have long suspected that those facial adjustments serve some evolutionary purpose, but the mechanism has been unclear for over a century.

Now, a study presents an answer that seems rather obvious in retrospect. Those wide-open eyes and flared nostrils take in more sensory information, which helps when you’re trying to figure out how to evade swiping bear claws.